1. Field
The invention relates in general to medical diagnostic devices and methods in the field of human health. The invention more specifically applies to diagnostic of autonomic neuropathy, and in particular to diabetic polyneuropathy.
2. Description of the Related Art
Diabetic polyneuropathy (DPN) is partly a peripheral autonomic neuropathy (PAN) that is linked to lesions of small unmyelinated fibres. These unmyelinated fibers, including those that innervate the sweat glands, are the first to undergo damage. As such, DPN is a nerve-length-dependent process that firstly affects the feet.
Peripheral autonomic neuropathy (PAN) results in the atrophy of sweat glands and decreased sudomotor response that may affect the skin suppleness and flexibility that prevent skin cracks and ulceration, and may also reduce sweating, leading to abnormal skin conditions such as dryness, fissures and blisters.
Moreover, PAN results in decreased foot sensitivity. The prevalence of PAN has recently been estimated to affect 43% of diabetic patients aged 40-70 years. Early detection of symmetrical distal sensory—motor DPN can decrease morbidity and the risk of foot complications.
Sensory function is considered one of the major initiating risk factors in the pathogenesis of diabetic foot ulcer. As no gold standard is available for early diagnosis of DPN, vibration perception threshold (VPT), using a biothesiometer, and pressure perception, using Semmes-Weinstein monofilaments, have been proposed to identify patients at risk, but none of these investigates peripheral autonomic involvement.
Peripheral autonomic neuropathies such as DPN are also usually evaluated through sudomotor function, using the sympathetic skin response (SSR), or by quantitative sudomotor axon reflex testing (QSART). These methods require specialized training to perform and are also time-consuming procedures. Neuropad® is another alternative test targeted for use by the patient, although it is less sensitive and semi-quantitative.
Thus, the need for highly trained personnel, lack of sensitivity, non-quantitative results and time required to take measurements have restricted the widespread use of sudomotor function assessment in clinical practice. There is therefore a need for an alternative method for detecting peripheral autonomic neuropathies such as diabetic polyneuropathy through assessment of sudomotor function.